Abstract:
This paper presents detailed results of new lanthanum tellurite synthesis and its heat capacity calorimetric research.
For the first time, a triple lanthanum tellurite was synthesized by the solid-phase method from oxides
of lanthanum, nickel (II), tellurium (IV) and calcium carbonate. The generation of the equilibrium composition
of the synthesized compound was controlled by the method of X-ray diffraction analysis (XDA) on the
diffractometer DRON-2.0. By the results of the XDA it was established that there was synthesized a triple
lanthanum tellurite La2CaNiTeO7. Heat capacity at constant pressure of the synthesized tellurite was
researched by the method of dynamic calorimetry at the range of 298.15–673 К. Based on the experimental
data, the equations, describing dependencies of heat capacity of the compound on temperature were
calculated. When studying the temperature dependences of the heat capacity of La2CaNiTeO7, abnormally
sharp λ-like peaks probably associated with second-order phase transitions, were observed at 423 K.
Temperature dependencies of thermodynamic functions of La2CaNiTeO7 Sº(T), Hº(T)–Hº(298,15), Фхх(Т)
were calculated based on the experimental data Срº(Т) and the calculated value Sº (298.15).
